COATING COMPOSITION AND METHOD FOR ITS PREPARATION

Abstract: The object of the invention is a coating mixture for interior walls, which is applicable by spraying, which contains substantially finely divided cellulose fiber as a filler, cellulose or starch based binder, water and foaming agent, wereby the mixture can contain also small amounts of additives or adjuvants, and the amount of binder calculated from the cellulose fiber is 3 to 15 % by weight, and the dry matter content of the mixture is higher than appr. 12 % by weight. The invention also relates to a method for the preparation and application of the coating mixture.

Description: Coating composition and method for its preparation The object of the invention is a coating mixture which contains cellulose fiber and binder in a mixture with water. The invention also relates to a method for the preparation and application of the coating mixture. A great variety of sprayable wall coatings are known in the building industry. The use of cement as a binder is common to these solutions. The cement makes the finished coating resemble plaster, which i.a. for reasons of appearance considerably limits the use of the coating. Furthermore, the surface is hard and inelastic, and crumbles easily, and it does not stick to all building materials. Coatings are also known, for example from the US-publica¬ tion 4,994,509, which as a filler contain cellulose fibers together with a second, for example colouring filler com¬ ponent, such as quartz powder. However, the use of addi- tional fillers, especially in large amounts, makes the aqueous coating mixture hard and difficult to handle, and it cannot be applied by spraying without problems. The aim of the invention is to provide a sprayable mass containing natural fibers and binder, which may be used as a porous interior wall and ceiling coating in place of e.g. a sprayed plaster coating, conventional wall paper or the like. The object is thus to obtain a spreadable coating for such applications where also a sound absorbing coating is desired. In order to achieve this object, the filler com¬ ponent of the coating according to the invention consists of finely divided cellulose fibers, without mineral and other additional fillers. The coating composition according to the invention is thus characterized in that it contains - finely divided cellulose fibers as a filler, - water soluble cellulose and/or starch based binder, - water, as well as - foaming agent, and that the amount of binder calculated from the cellulose fibers is from 3 to 15 % by weight, and the combined dry matter content of cellulose filler and binder of the mixtu- re is higher than approximately 12 % by weight. By using, in the coating mixture, cellulose fibers, espe¬ cially cotton fibers, as the only filler, a porous and easily finishable coating is obtained, which in addition has excellent sound dampening properties. In the coating mixture according to the invention, the amount of binder calculated from the cellulose filler is from 3 to 15 % by weight, especially from 3 to 11 % by weight. The dry matter content of the filler and the binder in the mixture is advantageously higher than 15, such as 15 to 25, especially in the range of 15 to 20 % by weight, as calculated from the whole mixture. As the cellulose fiber, for example, finely divided cotton cellulose fibers may be used, which are commercially avai¬ lable in almost 100 % pure form and bleached. Other suita¬ ble cellulose fiber products comprise wood cellulose fiber, flax cellulose fiber, as well as other possible cellulose fiber products of vegetable origin, as well as fiber pro¬ ducts of regenerated cellulose, such as viscose. As a binder both water soluble cellulose based binders, such as cellulose ethers, for example methylcellulose, hydroxypropyl- and hydroxyethylcellulose, and especially carboxymethylcellulose, CMC are suitable. Said cellulose derivatives are commercially available. A second binder class is formed by cold water soluble starches and starch derivatives. The amount of binder to be used in the mixture according to the invention depends on the viscosity of the binder and on the desired adhesion, but the range mentioned above is generally suitable. CMC is commercially available, a suitable grade being for example Finnfix 300, manufacturer Metsa-Serla, wherein the CMC is in the form of the Na-salt of CMC. The type of foaming agent to be used in the mixture is not critical, but per se known surface active agents may be used in the mixture, such as anion active, cation active and non-ionic surface active agents, i.e. tensideε. Anion active tensides are i.a. alkylbenzene sulfonates, alkane sulfonates, fatty alcohol sulfates and fatty alcohol ether sulfates, advantageously long chain alkylsulfate salts, such as sodium laurylsulfate, and" soaps. Non-ionic tensides are i.a. ethoxylated fatty alcohols, fatty amines, fatty acids and fatty acid esters, and aminoxides. The amount of foaming agent is such which gives a suitable foaming ef- feet. The amount needed is usually small, and typically good results are obtained using amounts which are from about 0.001 to 1 % by weight, advantageously 0.001 to 0.2 and especially 0.01 to 0.1 % by weight calculated from the whole mixture. Without the use of foaming agent, a problem is the presence of excess water in the mass as well as obtaining a homo¬ genous mass. Without foaming agent, for one kilogram of dry matter about 9 to 11 litres of water are needed, whereas the said amount decreases to about half in the presence of foaming agent. The use of foaming agent thus accelerates the drying of the sprayed mass, the coating becomes porous and its coating capacity improves and the dried coating achieves a pleasant appearance. The foam producing surface active agent makes the mass airy and it is thus capable to take up more fibers forming a homogenous sprayable mass. Although according to an advantageous embodiment of the invention the composition consists essentially only of a cellulose filler of the above type, a binder, water and foaming agent in the said amounts, according to the inven¬ tion it is possible to use, in the composition, further adjuvants which typically are pigments, dye pastes and dye flakes, agents for improving moisture resistance and fire resisting agents. The total amount of these additional substances calculated from the whole mixture is relatively small, usually less than about 5 %, often less than 3 % by weight calculated from the whole mixture. The coating according to the invention dampens sound re¬ flection and can thus be used to improve the acoustical properties of a space. It has also heat insulating proper¬ ties. The coating is non-toxic, odorless and breathing. It does not form an air-impenetrable film on the surface of the structure. When coating surfaces which already possess sound dampening properties, such as mineral wool boards or a wall made from light aggregate bricks without a finishing layer, their sound dampening properties only increase. When coating mineral wool boards a continuous seamless surface is obtained. When sprayed onto a hard surface, the coating corresponds to its sound dampening properties to a thick textile carpet. The coating according to the invention functions, in addi- tion to dampening the sound, also as a collector of water of condensation. In this case the mass to be sprayed should include also agents having an inhibitory effect on the formation of bacteria and moulds. The coating can be made fire resistant by using fire resis- ting agents in the formulation. Thus a fire resisting agent in the form of a salt or salt solution, such as e.g. a nitrogen-phosphorus based solution (for example Amgard TR) is added to the mixture. The coating can be made comple- tely fire proof, the ignitability classification being 1 and the flame spread classification being 1. The moisture resistance of the coating may in turn be improved by adding resin to the mixture, or by substituting part of the binder for a suitable resin, such as aerylate or polyurethane dispersions. The colour of the naturally white coating may be changed by adding pigments or water soluble dye pastes, or various dye flakes. The natural yellowing of a white coating may be prevented by adding titan dioxide pigments at the preparation stage. The mass is prepared by simply mixing the binder in water using efficient mixing. Thereafter the foaming agent and the fiber, while still mixing, for example at a rate of 100 rpm, and optional adjuvants are added. The coating is rapidly and easily worked. The mixture is sprayed using a pump/spray combination which is capable of spraying a thick and airy mass. The structure of the surfa- ce may be varied by adjusting the sprayer pressure and the size of the nozzle. When an especially smooth surface is desired, the spraying is carried out twice. The second spraying is done onto the dried sprayed surface and smoot¬ hed with a spatula. The coating may also be applied di- rectly using a spatula or a spatula may be used for filling irregularities in the support material (for example when repairing acoustical mineral wool boards) . The coating does not require complicated priming work. By means of the coa¬ ting according to the invention also curved supports such as pillars, vaulted ceilings and the like may be coated. In the following the invention is described in more detail by means of the following examples and tests, which are not limiting to the invention. EXAMPLE A sprayable mass was prepared using the following recipe A): 20 1 water 350 g CMC 3.2 kg bleached finely ground cotton cellulose 12 g sodium laurylsulfate The CMC was mixed with water and the foaming agent was added. The ground cotton cellulose was added while con- tinously stirring. The same procedure was repeated but using in place of the mentioned amounts of cellulose and CMC B) 150 g CMC and 3.8 kg of cellulose fibers, and correspondingly C) 360 g CMC and 4.2 kg of cellulose fibers. The mixture according to the Example 1A) was sprayed on a support with a fiber coating spray device using a suffi¬ cient sprayer pressure. The fiber mass was sprayed onto different supports according to the table 1. In the sample 1, the spray support was concrete, in the sample 2 it was chip board, in the sample 3 it was gypsum board and in the sample 4 an acoustical wool board. Fracture strength was studied using a gypsum board sample (sample 5, table 2) , in which an artificial fracture had been made by placing two gypsum boards with their edges against each other prior to coating. The test specimens were allowed to condition under standard conditions (23 °C, 50 % RH) . Thereafter the adhe- rence of the coating to the support was measured by pulling test bodies glued to the surface (diameter 28 mm) vertical¬ ly upwards. The results of the test are given in table 1. Table 1. Results from the adherence tests of the fiber coating Sample Sup¬ Test Adhesion Break point port nr strength nr MPa 1 conc¬ 1 0.19 Border surface rete 2 0.20 between coating 3 0.21 and concrete 4 0.22 — II _ 5 0.26 — II — mean 0.2 — II — 2 chip 1 0.24 Border surface board 2 0.28 between coating 3 0.28 and chipboard 4 0.31 — II — 5 0.29 — II — mean 0.3 3 gypsum 1 0.23 Border surface board 2 0.27 between coating 3 0.20 and gypsum board 4 0.23 — H _ 5 0.23 — li ¬ mean 0.2 4 acous¬ 1 0.005 the wool tical 2 0.006 sheared wool*) 3 0.007 — H _ 4 0.008 — M — mean 0.007 *) As opposed to the other samples, the test body was square with a side length of 1 = 44 mm. The fracture strength was tested with the sample 9. From the sample two test bodies with a width of appr. 50 mm were cut. The test bodies were pulled to fracture at a rate of 0.5 mm/min. The results are shown in the table 2. Table 2. Results of pull tests Test sample Tensile The width of the frac¬ strength ture at the breaking N/50 mm of the coating, mm 1 225 1 1 300 1 From the table 1 it may be seen that the coating has a good adherence to most supports. The best adherence 0.3 MPa was obtained to chipboard. From the result of the table 2 it is seen that the coating has a good fracture strength. The absorption ratios of a board coated with a cotton fiber coating according to the invention have been determined using the ISO-standard 354-1985. The thickness of the coating was 4 - 6 mm and the board to coated either a 0.7 mm profile metal plate or a 13 mm gypsum board, or alterna¬ tively the thickness of the coating was 3 - 4 mm on a 50 mm acoustical board. Good absorption measurement results were obtained, for example a coating sprayed onto gypsum board corresponds to its sound attenuating properties to a thick textile carpet. When sprayed onto acoustical wool, the sound absorbing properties of the acoustical wool did not weaken but improved. The invention is not limited to the afore mentioned embodi¬ ment but may be varied within the scope of the appended claims.

Claims: Claims 1. Coating mixture, characterized in that is contains - finely divided cellulose fiber as a filler, - a water soluble cellulose and/or starch based binder, - water, and - foaming agent, and that the amount of the binder calculated from the cellulose fibers is 3 to 15 % by weight, and the dry-matter content of the cellulose filler and the binder of the mixture is together higher than appr. 12 % by weight. 2. Coating mixture according to claim 1, characterized in that the amount of binder calculated from the cellulose filler is 3 to 11 % by weight, and the dry-matter content of the mixture is higher than 15, especially 15 to 20 % by weight. 3. Coating mixture according to claim 1 or 2 , characterized in that the cellulose fiber is cotton fiber. 4. Coating mixture according to any one of the claims 1 to 3, characterized in that the binder is a cellulose ether, especially carboxymethylcellulose. 5. Coating mixture according to any one of the claims 1 to 4, characterized in that the it, as a foaming agent, con¬ tains a long chain alkylsulfate salt, especially sodium laurylsulfate. 6. Coating mixture according to claim 5, characterized in that the amount of foaming agent is appr. 0.001 to 1 % by weight, especially 0.01 to 0.1 % by weight, calculated from the whole mixture. 7. Coating mixture according to any one of the preceding claims, characterized in that the formulation in addition contains fire resisting agents, pigments, dye pastes and flakes, or moisture resisting agents, the total amount of such agents being at the most 5 % by weight, especially at the most 3 % by weight, calculated from the whole mixture. 8. Coating mixture according to claim 1, characterized in that it consists of - appr. 10 to 20 % by weight of cellulose fibers, - appr. 0.5 to 2.5 % by weight of binder, - appr. 0.005 to 0.2 % by weight of foaming agent, - 0 to appr. 5 % by weight of further adjuvants, espe¬ cially fire resisting agent, the remaining part of the mixture consisting of water. 9. Coating mixture according to claim 1, characterized in that it consists of the following components - 12 to 18, especially appr. 16 % by weight of cellulo- se fibers, especially cotton cellulose fibers, - 1.0 to 1.5, especially appr. 1.5 % by weight of carboxymethylcellulose, and - 0.01 to 0.1 % by weight of foaming agent, and - 0 to appr. 3 % by weight of further adjuvants, the remaining part of the mixture consisting of water. 10. Method for the preparation of a coating mixture, cha¬ racterized in that finely divided cellulose fibers and cellulose or starch based binder are mixed together in water in the presence of a foaming agent, and optional adjuvants are added. 11. Method according to claim 10, characterized in that first the binder is added to the water while vigorously stirring, thereafter the foaming agent, the cellulose fiber and optional adjuvants are added while vigorously stirring to form an airy homogenous mass. 12. Use of a coating mixture according to any one of the claims 1 to 9 for the coating of interior walls, characte¬ rized in that the coating takes place by applying the airy coating mixture by spraying. 13. Use according to claim 12 for the preparation of sound absorbing coated interior walls.

Inventors: TAMPIO ANNA-LIISA, TAMPIO, ANNA-LIISA
Applicants: TAMPIO ANNA LIISA, TAMPIO, ANNA-LIISA
Application year: 1994
Main classification: C09D101
IPC codes: C09D101, C09D103, E04F13